In recent years, as the airtightness in living space increases, there has been an increasing demand for the development of a technique to realize clean and comfortable living space, particularly a technique to purify the air inside the living space. For the purification of the air, conventionally, there are widely used air purifiers which are designed to produce a circulating air flow by sucking the air inside a target space and discharging the air through a suitable filter, and to catch floating substances present in this circulating air flow successively with the filter.
However, in this kind of air purifiers, floating substances are removed only from the air sucked into the main body, and thus it is difficult to give the air purifying effect throughout the living space. For example, there are problems that the air tends to stagnate behind furniture in a room, at the corners of a living room, or the like, and a sufficient effect cannot be expected in areas where air purification is necessary. Moreover, in order to maintain the satisfactory performance, cleaning and replacement of the filter are essential, and consequently there is a problem that complicated maintenance work including such cleaning and replacement must be performed.
Furthermore, the floating substances in the living room include particulates such as dust and smoke particles, and bacteria such as fungus and coli bacteria. Air purifiers using a filter as mentioned above are effective against the former matter (particulates) and can give a predetermined removal effect, but have a problem in terms of the latter matter (bacteria) harmful to human body, that is, a sufficient removal effect can not be obtained because the bacteria breed under the condition of being caught in the filter and are returned into the living space together with the circulating air flow. In recent years, air purifiers that improve the bacteria removal effect by using a filter made of antibacterial material have been put to practical use, but, in actual circumstances, satisfactory performances are not obtained.
In order to solve such problems, the applicant of the present application proposed a purifying method based on a new concept, in which the air in a space is purified by discharging ions into the space. This method is implemented by positioning an ion generator for generating substantially equal amounts of positive ions and negative ions, in the middle of a passage for discharging a flow of air into a target space, and discharging the positive ions and negative ions together with the flow of air into the target space.
Positive ions and negative ions are generated by ionizing moisture in the air by plasma discharge, and have a form in which a plurality of water molecules attach around hydrogen ions (H+) or oxygen ions (O2−), i.e. the form of cluster ions. The ions discharged into the air gather around the floating particles, mutually cause a chemical reaction, make hydrogen peroxide H2O2 or hydroxy radical •OH as active species, carry out an oxidation reaction for removing hydrogen from the floating particles, inactivate the floating particles, and disinfect the floating bacteria.
Air purification as mentioned above is carried out by the function of ions which are discharged into the target space and spread throughout the space, and these ions act on the floating bacteria to disinfect them and further act on foul-smelling molecules and harmful molecules to make them odorless and harmless, thereby obtaining a satisfactory purification effect over the entire target space. Moreover, since the cluster ions discharged into the space are ions which are present in the natural world, harmless to human body and change to H2O (water) by oxidation reaction, there is no possibility that the cluster ions cause environmental pollution.
As described above, the ion generator for use in air purification performs the function of disinfecting floating bacteria, the function of making foul-smelling substances odorless, and the function of making harmful substances harmless. Therefore, there has been great demand for the application of the ion generator not only to air purifiers, but also to the whole range of electric apparatuses dealing with a flow of air, such as air conditioners, refrigerators and cleaners.
This ion generator comprises an ion generating element which has a discharge electrode and an induction electrode disposed to face each other with a dielectric therebetween and performs plasma discharge by application of a high-voltage AC driving voltage between the electrodes. This ion generating element can be constructed in a compact cylindrical shape in which the two electrodes are disposed on the center of the axis and the circumferential surface of a cylindrical dielectric, or in a compact plate shape in which the two electrodes are disposed on both surfaces of a plate-like dielectric. However, when this ion generating element is to be operated as the ion generator, it is necessary to provide booster means and a circuit substrate to increase the input voltage from a commercial power supply and generate a driving voltage having a predetermined driving waveform, and also necessary to ensure that their installed positions are mutually insulated. Thus, there are problems that it is difficult to apply this ion generating element to electric apparatuses other than those which were designed on the supposition that the ion generating element is to be incorporated into them, and the application range is limited.